I have a hard time taking seriously any argument that this guy wasn't justified in using his pistol, or that his shooting the assailant here didn't help the stabbing victim - it sounds like it may well have saved her life.
In the main, the nonbiased studies on implementation of liberal concealed-carry laws (not that there are many nonbiased studies on such a polarizing issue) seem to indicate little net gain or reduction in crime, although I suppose there's a significant amount of positive and negative behavior done by CCW permit holders that goes unreported.
I like guns and own them, but have never had much interest in carrying - it seems to me the liabilities outweigh the benefits for the most part. Actually, I recall a contributing member of the Glock Talk bulletin board, which I used to frequent quite often, was killed when he tried to use his legal concealed pistol against a liquor-store robber.